Continuity mistake: In the scene in Jameson's office after he throws his cigar out the window and the Goblin throws it back, when Jameson is looking at the cigar on his desk, he is sitting at an angle. Right before the Goblin crashes in, Jameson is sitting perfectly straight at the desk, with both hands on the desktop. (01:11:50)
Continuity mistake: When MJ and Peter are discussing the beating that Peter gave Flash that morning in school, MJ says, "He's just glad you didn't give him a black eye for graduation." This scene takes place the day after Peter was bitten by the spider, when the weather is cold. High school graduations generally take place in June or late May - so any black eye Peter might have given Flash would long be healed up by graduation. (00:29:15)
Continuity mistake: During the scene where the apartment building is on fire - a woman points directly up and exclaims, "Look up there!" while Spider-Man is still swinging towards the fire from several blocks away. (01:19:00)
Continuity mistake: In the scene where Osbourne tries the performance enhancers on himself, he takes off his labcoat and throws it into a corner. We see a long shot of the lab, and the coat is in at the base of the pillar. In a subsequent long shot however, the coat has moved a foot or so. (00:14:45)
Continuity mistake: During the scene in which Peter is introduced to Norman Osborn in front of the museum, keep an eye on the Volvo parked behind the Rolls Royce. When the camera first faces Mr. Osborn (Willem Dafoe), the Volvo in the background has the window rolled halfway down. Camera switches to Peter and Harry, then back to Mr. Osborn. This time the window is all the way up. When the camera comes back to Mr. Osborn again, there is someone leaning in the window talking to the driver. The next time the camera comes back to Mr. Osborn, the window is again halfway down. (00:05:54)
Continuity mistake: When Uncle Ben's killer enters the warehouse he reloads his gun and pulls the slide back to cock it. Later, when he points the same gun at Peter, you can hear the distinct sound of the hammer being pulled back. However, despite cocking the gun twice, you can see that the gun is not cocked. (00:46:25)
Continuity mistake: When Peter runs downstairs the morning after his bite, Uncle Ben is startled from drinking his coffee. From the front angle, Uncle Ben is holding the cup with two hands. When he turns to look at Peter and the angle changes, he's holding the mug with only one hand. (00:19:08)
Continuity mistake: When Osborn is getting ready to radiate himself at his laboratory, he drinks the small bottle of anti-coagulant before stepping into the chamber. He then smashes the bottle on the ground to his left. But in later shots you see no evidence of the fragments of the glass bottle. (00:15:35)
Continuity mistake: In the final battle scene, Goblin's costume alternates between clean (green) and dirty (white/dusty) throughout the scene. (01:41:30)
Continuity mistake: When Parker is chasing the robber into the abandoned warehouse, you see a shot of the robber holding the gun in his left hand and carrying the money bag in his right hand. However, the next shot you see him load a clip into the gun with the bag in his left hand and the gun in his right hand. (00:45:25)
Continuity mistake: In the scene where Spidey is stopping the armored car robbery, he dispatches several thugs with some fancy, acrobatic fighting. When he lands, a money bag is visible in front of him that wasn't there in the wide shot. (00:58:30)
Continuity mistake: When Peter wakes up the day after he was bitten by the spider and goes to the living room doing a little "stunt", Uncle Ben immediately turns to him, but in the next shot he makes a forward movement as Peter falls on the ground after the stunt.
Continuity mistake: When Peter tries his first web swinging on the rooftop, the sky turns from sunny to cloudy between shots.